Find Simple Closed Path for a given set of points

// A C++ program to find simple closed path for n points // for explanation of orientation() #include <bits/stdc++.h> using namespace std; struct Point {  int x, y; }; // A global point needed for sorting points with reference // to the first point. Used in compare function of qsort() Point p0; // A utility function to swap two points int swap(Point &p1, Point &p2) {  Point temp = p1;  p1 = p2;  p2 = temp; } // A utility function to return square of distance between // p1 and p2 int dist(Point p1, Point p2) {  return (p1.x - p2.x)*(p1.x - p2.x) +  (p1.y - p2.y)*(p1.y - p2.y); } // To find orientation of ordered triplet (p, q, r). // The function returns following values // 0 --> p, q and r are collinear // 1 --> Clockwise // 2 --> Counterclockwise int orientation(Point p, Point q, Point r) {  int val = (q.y - p.y) * (r.x - q.x) -  (q.x - p.x) * (r.y - q.y);  if (val == 0) return 0; // collinear  return (val > 0)? 1: 2; // clockwise or counterclock wise } // A function used by library function qsort() to sort // an array of points with respect to the first point int compare(const void *vp1, const void *vp2) {  Point *p1 = (Point *)vp1;  Point *p2 = (Point *)vp2;  // Find orientation  int o = orientation(p0, *p1, *p2);  if (o == 0)  return (dist(p0, *p2) >= dist(p0, *p1))? -1 : 1;  return (o == 2)? -1: 1; } // Prints simple closed path for a set of n points. void printClosedPath(Point points[], int n) {  // Find the bottommost point  int ymin = points[0].y, min = 0;  for (int i = 1; i < n; i++)  {  int y = points[i].y;  // Pick the bottom-most. In case of tie, choose the  // left most point  if ((y < ymin) || (ymin == y &&  points[i].x < points[min].x))  ymin = points[i].y, min = i;  }  // Place the bottom-most point at first position  swap(points[0], points[min]);  // Sort n-1 points with respect to the first point.  // A point p1 comes before p2 in sorted output if p2  // has larger polar angle (in counterclockwise  // direction) than p1  p0 = points[0];  qsort(&points[1], n-1, sizeof(Point), compare);  // Now stack has the output points, print contents  // of stack  for (int i=0; i<n; i++)  cout << "(" << points[i].x << ", "  << points[i].y <<"), "; } // Driver program to test above functions int main() {  Point points[] = {{0, 3}, {1, 1}, {2, 2}, {4, 4},  {0, 0}, {1, 2}, {3, 1}, {3, 3}};  int n = sizeof(points)/sizeof(points[0]);  printClosedPath(points, n);  return 0; }